Power supplies for electro-luminescent (EL) lamps or panels typically include inverters having a regulated or fixed output, or a tuned circuit for a single lamp or panel size. Tuned inverters typically can be optimized only for a single lamp size. In other words, the tuned circuitry requires the matching of the inverter to the size or surface area of the EL panel. Such tuned inverters can have some compensation for change in lamp load due to aging in that the drive signal current and voltage will rise slowly over time as the lamp ages in order to maintain power to the lamp. There are a number of drawbacks with prior tuned inverters. For example, the inverters cannot power a wide range of lamp sizes; therefore, it is necessary to inventory numerous different and distinct inverters to cover a reasonable range of lamp sizes. The inventory approach is both inefficient and uneconomical. Further, these tuned inverters provide only modest compensation for change in the lamp load due to aging. Such compensation only marginally improves half-life over inverters having regulated or constant or fixed outputs.
Regulated or fixed output inverters can power a range of lamp sizes, but have no load compensation for the EL lamp as it ages over its operating life. Therefore, the brightness half-life values of EL lamps powered by such fixed output inverters are relatively short. An additional drawback with both fixed output and tuned inverters is that most have been known to provide only DC voltage inputs, but not AC voltage inputs, such as at 115 VAC or 230 VAC. For large EL lamp sizes, AC voltage inputs are the only practical means of operation for the fixed output and tuned inverters.
There has been a recent demand for brighter electro-luminescent lamps even if such brighter lamps should result in a shorter total operating life. Furthermore, the market is demanding an electro-luminescent power supply, which operates over a range of lamp sizes without the above-mentioned disadvantages. Applicant's U.S. Pat. No. 6,043,609, titled, Control Circuit and Method for Illuminating an Electro-luminescent Panel represents an improvement over known EL power supplies.
Although applicant's above referenced EL power supply operates over a range of lamp sizes and provides voltage compensation due to aging of the EL lamp, the upper range of lamp size is limited to approximately 2,500 square inches. Larger size applications of EL lamps for example, up to 12,500 square inches or approximately 5 times the area that can presently be illuminated with applicant's EL power supplies cannot be accommodated.
A further disadvantage is the above and other known power supplies cannot typically operate for any appreciable length of time without circuit component damage or failure when operating into an open load or a shorted load condition both of which conditions are readily present in actual practice and usage. EL power supply failures due to open or shorted conditions are costly, not only because of damage to the power supply, but also due to lost revenues from unlit advertisements for example.
Also, known EL power supplies are typically protected by line fuses that only "blow" after their current ratings are exceeded or by internal fuses within the EL power supply. The reaction time of line fuses or internal fuses is generally too slow to prevent damage to the EL power supply or injury to a person in contact with the EL power supply or EL lamp. In order to restore operation of the EL power supply, an operator must access the EL power supply at its location. It is desirable therefore to provide protection for the EL power supply that has a fast reaction time to prevent damage to the EL power supply and which allows restoration of the EL power supply from a remote location.
A further disadvantage of known EL power supplies is the lack of an internal diagnostic aid to indicate and localize the likely faulty component area or circuit of the EL power supply.
The market is further demanding an EL power supply that operates from both AC and DC voltage power sources and has automatic detection and line voltage selection for 110 VAC or 220 VAC without operator intervention.
A further drawback with known EL power supplies is the inability to drive EL lamps to produce dimming or special effects as typically done with incandescent lights in theaters and other such locations. Such optional or special effect features are typically effectuated by means of a control panel which provides a standard industry encoded signal to cause the desired dimming, or dynamic display such as flashing or other rapid turning-on and turning-off of lights. Known EL power supplies lack an input interface to such industry standard control panels and typically do not react quickly enough to achieve the desired result.
Accordingly, it is an object of the present invention to provide a power supply or ballast, which operates from AC and DC power sources to illuminate a range of EL lamp sizes while providing load compensation to accommodate aging of the EL lamp.
It is another object of the present invention to provide a power supply for an electro-luminescent lamp, which operates from both AC and DC voltage power sources.
It is yet another object of the present invention to provide a power supply for electro-luminescent lamp that automatically detects and selects the required line voltage-operating mode.
It is yet a further object of the present invention to provide an internal diagnostic aid to identify and localize a likely faulty component area of the circuit.
It is yet another object of the present invention to provide protection for a power supply which is remotely resettable.
It is yet a further object of the present invention to provide a power supply to illuminate an EL lamp with special effects.